WO2001043857A1

WO2001043857A1 - Micromixer

Info

Publication number: WO2001043857A1
Application number: PCT/EP2000/012736
Authority: WO
Inventors: Wolfgang Ehrfeld; Volker Hessel
Original assignee: INSTITUT FüR MIKROTECHNIK MAINZ GMBH
Priority date: 1999-12-18
Filing date: 2000-12-14
Publication date: 2001-06-21
Also published as: DE50002879D1; DE19961257A1; EP1242171B1; EP1242171A1; DE19961257C2; ATE244596T1; US20030039169A1

Abstract

Micromixers constitute a main component of microreactors that have three-dimensional microstructures in a fixed matrix, in which chemical reactions take place. In said micromixer, fluids from their respective supply chambers are divided into spatially separate fluid streams using a network of microchannels allocated to the respective streams. Said streams then emerge as jets with identical volumetric flows for each fluid into a mixing chamber. The invention aims to ensure that identical volumetric flows are achieved for each fluid at the respective microchannel outflow and to produce a micromixer with a simple, compact construction. Wedge-shaped plates can be used as the supply elements (2a-d). Said plates can be assembled to form at least one ring sector which surrounds the mixing chamber (5) in the form of a curve. Alternatively, planar plates can be used which comprise a cavity in their central region, into which the microchannels (31-34) emerge, in such a way that the stacked plates form the mixing chamber (5). The microchannels (31-34) provided for each fluid form one or more symmetrical bifurcation cascades (3) comprising at least two stages. The micromixer can be used in microreactors, for example in the field of combined chemistry, for creating emulsion and gaseous/liquid dispersions and for gas-phase catalysis.

Description

micromixer

Description:

The invention relates to a static micromixer according to the preamble of claim 1. The invention also relates to a static micromixer according to the preamble of claim 15.

Micromixers form a main component of so-called microreactors, which have three-dimensional microstructures in a solid matrix in which chemical reactions are carried out. The microreactors are becoming increasingly important, for example, in combinatorial chemistry for the production of emulsions and gas / liquid dispersions and in gas phase catalysis.

In the micromixer, at least two fluids from their respective feed chambers are typically divided into spatially separated fluid streams by a respective assigned array of microchannels, which then exit as a fluid jet with the same volume flow for the respective fluid into a mixing or reaction chamber. Each fluid jet is guided adjacent to a jet of another fluid into the mixing and reaction chamber, in which the mixing takes place by diffusion and / or turbulence. It is important that identical volume flows of one fluid each are introduced into the mixing or reaction chamber through the microchannels, because otherwise there would be spatially different mixing ratios in the mixing or reaction chamber, which would falsify the mixing or reaction result. Since the volume flows through pressure drops in the microchannels are influenced, the microchannel systems must be designed in such a way that all microchannel branches have the same - and ideally low pressure loss.

A static micromixer is known from WO 95/30476, which provides a mixing chamber and a guide component for the separate supply of the substances to be mixed. The guide component consists of plate-like elements in the form of thin foils, each with a group of parallel, straight-line grooves, these plate-like elements being stacked one on top of the other. The grooves of the foils lying one above the other have a slope alternating with the longitudinal axis of the micro-mixer, so that the openings of the channels adjoining the mixing chamber are aligned one above the other and diverge on the fluid inlet side towards separate inlet chambers. The channels of the guide component each have the same length and thus the same flow resistance. However, since the fluids flow into the mixing chamber on different sides due to the oblique arrangement of the microchannels, the mixing effectiveness at the edge zones is lower than in the center due to the wall friction influence of the mixing chamber.

To increase the local effectiveness of the mixing, it is proposed in DE 195 40 292 Cl that the respective groups of grooves in the layers stacked on top of each other are curved in an arc and run alternately from the mixing chamber to one of the two feed chambers, so that all grooves are aligned parallel to one another open into the mixing chamber. To achieve equal flow resistances, it is stated that the sides of the guide component, which adjoin the feed chambers, are inclined so that the channels have an approximately equal length relative to the side adjoining the mixing chamber. To avoid curved entry surfaces, it is specified that the surfaces correspond to an approximation line to be determined according to a specified formula align. However, this only allows small arc angles of the grooves, so that an arrangement of the supply chambers on two opposite sides of the guide component or a separate supply of more than two fluids is hardly feasible.

The known microchannel systems have the disadvantage that special supply chambers are required and that all microchannels leaving the respective supply chambers have to be supplied with the respective fluid evenly, i.e. that the jet pressure of the inflowing fluids has to be homogenized. For this purpose, extensive feed chambers have to be provided, which can lead to space problems and increase the fluid retention time. Despite these feed chambers, a homogenization of the jet pressure is only guaranteed over a limited pressure range and thus volume flow range.

DE 35 46 091 C2 describes a cross-flow microfilter which is preceded or followed by an inflow distributor and a concentrate collector. Such an inflow distributor can be constructed in the form of a bifurcation structure, a number of curved partition walls corresponding to the number of bifurcation cascades being required to form the bifurcation structure.

In "A Microflow Reactor for Two Dimensional Investigations of In Vitro Amplification Systems" in Microreaction Technology; proceedings of the first international Conference on microreaction technology (Editor: W. Ehrfeld), Springer 1998, a microreactor is presented that has a collection chamber in a feed layer, into which two bifurcation cascades open opposite, through which a fluid is introduced. From there, the fluid enters a reaction chamber via a pressure barrier. In Chemische Technik 26, Vol. 1997, No. 1, pp. 131-134, microreactors for chemistry are described, which have a plurality of superimposed plates with a groove structure for the supply of the reactants. After passing through a heat exchanger section, a bifurcation cascade is provided behind the reaction and mixing area for the confluence of the individual streams.

The object of the invention is to provide a micromixer with microchannels at whose outlet there are identical volume flows for each fluid, the micromixer being distinguished by a simple and compact design.

This object is achieved in that the feed elements are wedge-shaped plates that can be assembled into at least one ring sector that surrounds the mixing chamber in an arc, and that the microchannels provided for each fluid have a symmetrical at least two stages i (i = 1 to n, with n > 2) Form a comprehensive bifurcation cascade.

This object is also achieved in that the feed elements are flat plates which have an opening in the central region into which the microchannels open, so that the stacked plates form the mixing chamber, and that the microchannels provided for each fluid have one or more symmetrical ones , form at least two stages i (i = 1 to n, with n> 2) comprising bifurcation cascades.

The successive division of a fluid stream into two equal partial streams, which in turn are divided into 2 + 2 = 4 equal partial streams and gradually further divided accordingly, has the consequence that all streams of a fluid are subjected to the same conditions and thus identical volume flows for each fluid the mixing or reaction chamber emerge. The division into partial streams, which are subject to the same conditions as possible succeed in reducing the cross-sections of the microchannels from stage to stage. Depending on the surface shape, the cross-sections can be reduced by reducing the width and / or depth or, in the case of round cross-sections, by reducing the radius. Especially in the case of wedge-shaped plates as feed elements, it is advisable to vary the depth, since in this way the volume available as the feed element is used well. The fact that all partial flows of a fluid are also fed from a storage chamber further contributes to the uniformity of the conditions.

Another advantage is that each bifurcation cascade starts from a single fluid flow (supply channel) which is connected to the storage chamber, so that no spatially extended supply chambers are necessary. The feed channels can be adapted much better to the respective local conditions, so that a compact micromixer can be realized.

Storage chambers can be arranged outside the micromixer at any point and in any number, so that the mixing of more than two fluids can also be carried out.

Also contributing to the compact design are the feed elements designed as wedge-shaped plates, which can be assembled to form a ring sector or even a closed ring. As the depth of the microchannels decreases towards the mixing chamber, the wedge shape can be used optimally. The microchannels with a large channel depth or cross-sectional area are arranged in the thicker area of the wedge-shaped plates and the microchannels with a small channel depth or cross-sectional area are arranged in the thinner area of the plates. In this way, the outlet openings of the microchannels of the last bifurcation stage can be placed close to one another in a complex construction. The mixing chamber can be rotationally symmetrical, preferably zy cylindrical are formed, which promotes the mixing of the fluids introduced into the mixing chamber.

Such mixing chambers of cylindrical shape are superior to the mixing chambers hitherto known from the above-cited documents in that the ratio of active to inactive area is greater, and thus the overall throughput and the mixing effectiveness are better. The active area is the area from which fluid flows emerge and the inactive area is the area from which no fluid flows emerge. In the case of the conventional, rectangular mixing chambers, one of six sides is used for the supply of fluids, while in the cylindrical mixing chamber the entire outer surface can be used.

The simultaneous use of bifurcation cascades as a fluid guide structure and wedge-shaped plates as feed elements results in a micromixer for carrying out reactions, the selectivity and reproducibility of which depend sensitively on the quality of the mixture.

The pressure loss within the microchannels of the i-th stage (i = 1 to n, n> 2) can be further minimized by changing the geometric dimensions of the microchannels of different stages relative to one another. The length of the microchannels towards the mixing chamber can be shortened (L, ₊ , <L, with L, = length of the microchannels of the i-th stage), it having proven advantageous to choose the lengths such that the ratio of the lengths two successive stages is constant. Such bifurcation cascades are called self-similar.

Particularly in cases in which the number n of stages is greater than or equal to 3, a preferred embodiment consists in reducing the dimensions of the microchannels from stage to stage only up to the penultimate stage. The bifurcation cascade can be self-similar up to the penultimate stage. At least one wedge-shaped plate preferably has grooves that form microchannels on at least one wedge surface. The micromixer can be assembled from several identical wedge-shaped plates, so that the manufacturing costs can be reduced.

According to a further embodiment, the wedge-shaped plate has a bifurcation cascade on each of the wedge surfaces, the microchannels of the last bifurcation stage opening at the end face of the wedge-shaped plate being arranged offset to one another in the circumferential direction of the mixing chamber, in order to minimize the distance.

In a further preferred embodiment, the wedge-shaped plate has grooves on both wedge surfaces which have a partial cross section of the microchannels. The grooves in the superimposed surfaces of two adjacent feed elements complement each other to form the full cross section of the microchannels. In this embodiment too, the micromixer can be assembled from several identical wedge-shaped plates, which leads to a reduction in manufacturing costs. In this way, otherwise difficult to manufacture, aerodynamic circular cross sections can be produced.

In a further embodiment, the microchannels are designed in such a way that the width and / or depth and possibly also the length of the nth stage, that is to say the last stage before it flows into the mixing chamber, is greater than in the stage before (stage n -1), ie the penultimate stage. This results in a higher ratio of active to inactive area based on the outer surface of the mixing chamber, which contributes to better mixing of the fluids. In principle, the grooves in the individual feed elements can be arranged offset to one another in such a way that if two fluids A, B were distributed alternately between the individual feed elements, a partial flow of the fluid B upon exiting into the mixing chamber of four Partial flows of the fluid A is surrounded and vice versa. If the cross-section of the microchannels, in particular the width and / or depth of the microchannels, is enlarged at the nth stage compared to stage n-1, it can be achieved that the exit surfaces of the fluids overlap in the axial or circumferential direction of the mixing chamber. With a sufficiently small distance between the exit surfaces, this increases the mixing contact surface and thus also the mixing effectiveness.

The bifurcation cascades for each fluid are preferably connected to a common feed channel. This helps to ensure the uniformity of the external conditions for the fluid flows of a fluid and thus increases the reproducibility of the mixture.

In order to be able to build the micromixer as compactly as possible, in a preferred embodiment the common feed channels are integrated in the form of bores in the feed elements or are introduced as grooves in the housing surrounding the feed elements.

The execution of the feed elements as flat plates with an opening in their center into which the microchannels open, so that the stacked plates together form the core of the micromixer, the openings lying one above the other forming the mixing chamber, allow the production of a particularly compact, stable, simple and micro mixer to be produced inexpensively. For the advantages of the bifurcation of the microchannels, reference is made to the previous explanations.

Annular plates are particularly preferred as feed elements. Through them one obtains mixing chambers of cylindrical shape, which have the advantage that the ratio of active to inactive area is larger and thus the overall throughput and the mixing effectiveness are better. The pressure loss within the microchannels of the i-th stage (i = 1 to n, n ≥ 2) is minimized by shortening the length of the microchannels towards the mixing chamber (L, ₊ , <L, with L, = length of the microchannels of the i -th stage). It has proven to be advantageous to choose the lengths such that the ratio of the lengths of two successive stages is constant. Such bifurcation cascades are called self-similar.

As with the wedge-shaped plates, the microchannels are preferably formed from grooves formed in the plates. The microchannels on one and the other side are advantageously arranged offset from one another. This reduces the distances and thereby increases the mixing effectiveness.

In a further embodiment, the grooves of each feed element have a partial cross section of the microchannels, the grooves located in the superimposed surfaces complementing the full cross section of the microchannels. These and the previous measures can reduce the manufacturing costs, since the micromixer can be assembled from several identical flat plates.

In order to be able to build the micromixer even more compactly, in a preferred embodiment the feed channels for the individual bifurcation cascades are integrated in the feed elements in the form of openings. It should be noted that openings should be provided in each flat plate for the feed channels, to which no bifurcation cascade is connected in this special plate. The micromixer can be constructed from identical feed elements which are rotated relative to one another in such a way that not only a continuous mixing chamber but also continuous feed channels are formed for each fluid. Exemplary embodiments of the invention are explained in more detail below with reference to the drawings:

Show it:

Figure la is a perspective view of feed elements with grooves forming microchannels on one side;

Figure lb is a perspective view of feed elements with grooves forming microchannels on both sides;

FIG. 1c shows a further perspective illustration of feed elements with grooves forming microchannels on both sides;

Figure 2a is a perspective view of inserted into a housing

Feed elements with feed channels above and below the feed elements;

Figure 2b is a perspective view of inserted into a housing

Feed elements with feed channels on the side of the feed elements;

Figure 2c is a perspective view of inserted into a housing

Feed elements with feed channels which are integrated in the feed elements;

3a shows a plan view of two feed elements which are designed as flat, annular plates;

Figure 3b-d different groove arrangements in feed elements, which are designed as flat, annular plates. FIG. 1 a shows a plurality of feed elements 2 a - d lined up in a ring sector in perspective. This results in a cylindrical mixing chamber 5, the lateral surface being formed by the end faces 23 of the feed elements 2a-d. These feed elements 2a-d are wedge-shaped plates which have grooves 24 serving as microchannels 31-34 on each wedge surface 22. A smooth wedge surface 21 covers the microchannels in the adjacent wedge surface 22. For the sake of clarity, only a groove 24 and a microchannel 31-34 are designated as examples.

In order to optimally utilize the wedge shape of the feed elements 2a-d, microchannels 31-34 and the feed channel 4 are designed such that they have different depths with the same width, the cross section being rectangular in FIG. After each bifurcation 36, the depth decreases from the outside towards the mixing chamber 5. The flow direction of the fluids is directed radially from the outside inwards. A coordinate system with the directions 1, b and t is shown for the wedge element 2d. The length of a microchannel is measured in the direction of 1, the width of a microchannel in the direction of b and the depth in the direction of t.

In the example shown in FIG. 1 a, the fluid guide structure 3 is designed as a four-stage bifurcation cascade. The fluid flow flows from a storage chamber outside the device into the feed channel 4. This feeds into two microchannels 31 of the first stage, so that the fluid flow is divided into two equal partial flows. Both microchannels 31 of the first stage bifurcate into two microchannels 32 of the second stage, which means that on the second stage the original fluid flow is divided into four partial flows. This symmetrical bifurcation is continued in the example shown up to the fourth stage and results in the division of the fluid stream into 2 ′ partial streams, which pass from the microchannels 34 to the fourth stage Mixing chamber 5 open and can mix there with the partial flows from the other feed elements.

In Figure la, the grooves 24 in the feed elements 2a-d are arranged offset such that, assuming fluid A flows in feed elements 2a and c and fluid B in feed elements 2b and d, a partial flow of fluid B exits the mixing chamber 5 is surrounded by four partial flows of fluid A and vice versa. This contributes to the better mixing of the two fluids.

A further example of the configuration of the feed elements 2 is shown in FIG. 1b. In this case, grooves 24 are provided on both partial surfaces 21 and 22, which have a partial cross section of the microchannels 30. When two wedge surfaces 21 and 22 are placed against one another, two opposite grooves 24 complement each other to form the full cross section of a microchannel 30. Furthermore, the cross section of the microchannels 30 is rounded. Since in this case too the depth of the microchannels 30 decreases towards the inside with a constant width, the microchannels 30 have a round cross section directly in the mixing chamber 5. For better clarity, only one groove 24 and the microchannels 30 of a partial flow are also designated in FIG. 1b.

FIG. 1c shows a further exemplary embodiment of the feed elements 2. In this case, both the depth and the length of the microchannels 30 increase from stage i to stage i + 1, but from stage n-1 to stage n, ie the last stage before it flows into the Mixing chamber 5, both dimensions increase again. This is also shown in the enlargement of the cut feed element 2 '. The feed element 2 'is cut along the cutting surface 25 in such a way that a microchannel 30 is cut to a constant half width. The depth and length of the fourth-stage microchannel 34 are significantly greater than the depth and length of the third-stage microchannel 33. The mixing chamber therefore has a higher ratio of Fluid exit surface to total surface area, which increases the mixing effectiveness. As in FIG. 1 a, the individual grooves 24 are arranged with respect to one another such that a partial flow of a fluid can be surrounded by four partial flows of another fluid. The great depth of the fourth stage microchannels 34 results in an overlap of the exit surfaces in the circumferential direction of the mixing chamber. This increases the

Mixing contact surface of the fluids exiting into the mixing chamber 5 and thus also the mixing effectiveness.

In Figure 2a, the feed elements 2 are fitted into the housing 1, the housing 1 consisting of two circular disks into which recesses for inserting the feed elements 2 and for forming the mixing chamber 5 are incorporated, feed channels 4a and b, are above and below the feed elements 2 arranged in a ring around the housing 1 in one of the two circular disks, a fluid discharge channel 6 is arranged such that it opens centrally into the lower end face of the mixing chamber 5.

Figure 2b shows another embodiment of the housing 1, in which both supply channels 4a and b are in the same circular disc as the fluid discharge channel 6 and run laterally around the supply elements in the housing 1.

Figure 2c shows a further embodiment for both the housing 1 and the feed elements 2. In this case, the annular circumferential feed channels 4a and b are not in the circular plates forming the housing 1, but are integrated as holes in the feed elements 2 and run there ring-shaped around.

Figure 3a shows two feed elements 2, which are each formed as a flat, annular plate 2a, b. The plate 2b has a circular opening 7 in its center. They are circular on their circumference Openings are arranged, which form the feed channels 4a and 4b for the fluids A and B. The feed channels 4b of the plate 2b are connected to bifurcation cascades 3. A microchannel of first stage 31 emanates from each feed channel 4b and, after a bifurcation 36, is divided into two microchannels of second stage 32, each of which in turn is divided into 2 + 2 microchannels of third stage 33, etc. The lengths of microchannels 31 to 34 take with increasing level. The flat plate 2a is identical to the flat plate 2b. However, it is rotated by 45 ° to plate 2b. As a result, the feed channels 4a of the plates 2a and 2b and the feed channels 4b of the plates 2a and 2b come to lie on one another. Bifurcation cascades 3 for the fluid A depart from the feed channels 4a in the plate 2a. Stacking a plurality of plates 2a and 2b on top of one another results in a cylindrical micromixer.

FIGS. 3b to 3d show how the grooves 24 forming microchannels 30a, 30b can be arranged in the top 26 and / or the bottom 27 of a feed element designed as a flat plate 2 or 2a, b. For the sake of clarity, the plates 2, 2 a, 2 b are shown spaced apart in FIGS. 3b to 3d. For reasons of stability, however, it can also be considered to introduce additional spacer elements between the feed elements, but which would have openings for forming the mixing chamber and the feed channels but no bifurcation cascades.

In Figure 3b, the grooves are formed on the top 26a and 26b in both the plate 2a and in the plate 2b. The grooves in plate 2a form microchannels 30a for fluid A and the grooves in plate 2b form microchannels 30b for fluid B. The grooves in both plates are arranged such that microchannels 30a and 30b lie exactly one above the other.

The groove arrangement in Figure 3c differs from the groove arrangement in Figure 3b only in that the microchannels 30a and 30b to each other are staggered. It is thereby achieved that the microchannel for one fluid is surrounded by four microchannels for the other fluid. This increases the mixing effectiveness.

The feed elements 2 from FIG. 3d have grooves 24 on their upper side 26 and on their lower side 27. The grooves 24 each have a partial cross section of the microchannels 30a and 30b and complement each other to form the full cross section of the microchannels 30a, 30b in the superimposed surfaces 26 and 27. Therefore, the grooves on the top 26 are offset from the grooves on the underside 27. If the partial cross sections of the one side are used for one fluid and the partial cross sections of the other side for the other fluid, this again ensures that a microchannel 30a or 30b for the one fluid is surrounded by four microchannels 30b or 30a.

reference numeral

Housing a, b, c, d, 2 'feed element

Fluid guide structure a, b feed channel A, B

mixing chamber

Fluid discharge passage

perforation

wedge surface

front

groove

section

top

Bottom a, b microchannel A, B

First stage microchannel

Second stage microchannel

Third stage microchannel

Fourth stage microchannel

bifurcation

Claims

claims

1. Static micromixer with feed chambers for at least two fluids to be mixed, of which microchannels lead to a mixing chamber, the microchannels being arranged in at least two adjacent feed elements, characterized in that

that the feed elements (2) are wedge-shaped plates, which can be assembled into at least one ring sector which surrounds the mixing chamber (5) in an arc, and

that the microchannels (30) provided for each fluid form a symmetrical bifurcation cascade comprising at least two stages i (i = 1 to n, with n> 2).

2. Micromixer according to claim 1, characterized in that the cross section of the microchannels (30) decreases from stage to stage.

3. Micromixer according to claim 1 or 2, characterized in that the length of the microchannels (30) decreases from stage to stage.

4. Micromixer according to one of claims 1 to 3, characterized in that the bifurcation cascade is self-similar.

5. Micromixer according to claim 1, characterized in that the cross section of the microchannels (30) decreases up to level n-1 from level to level.

6. Micromixer according to claim 1 or 5, characterized in that the length of the microchannels (30) decreases from level to level up to level n-1.

7. Micromixer according to one of claims 1 to 6, characterized in that at least one wedge-shaped plate on at least one wedge surface (21, 22) has microchannels (30) forming grooves (24).

8. Micromixer according to claim 7, characterized in that the wedge-shaped plate on both wedge surfaces (21, 22) each has a bifurcation cascade, with the micro-channels (30) of the last Bi urcation calls opening at the end of the plate being arranged offset to one another.

9. Micromixer according to one of claims 7 or 8, characterized in that the grooves (24) of each feed element (2) have a partial cross section of the microchannels (30) and the grooves (24) located in the superimposed surfaces complement each other to the full cross section of the microchannels ,

10. Micromixer according to one of claims 5 to 9, characterized in that the cross section and / or the length of the microchannels (30) increases from level n - 1 to level n.

11. Micromixer according to one of claims 5 to 10, characterized in that the microchannels (3a) opening into the mixing chamber (5) overlap in the circumferential or axial direction of the mixing chamber (5).

12. Micromixer according to one of claims 1 to 11, characterized in that the bifurcation cascades for each fluid are connected to a common feed channel (4a, b).

13. Micromixer according to claim 12, characterized in that the common feed channel (4a, b) is arranged in the feed elements (2).

14. Micromixer according to claim 12, characterized in that the common feed channel (4a, b) is arranged in a housing (1) surrounding the feed elements (2).

15. Static micromixer with feed chambers for at least two fluids to be mixed, of which microchannels lead to a mixing chamber, the microchannels being arranged in at least two feed elements lying one on top of the other or spaced apart by one or more intermediate element (s), characterized in that the feed elements ( 2) are flat plates which have an opening (7) in the central area, so that the stacked plates form the mixing chamber (5) and that the microchannels (30) provided for each fluid have one or more symmetrical, at least two stages i ( i = 1 to 1, with n> 2) form comprehensive bifurcation cascades.

16. Micro mixer according to claim 15, characterized in that the flat plates are annular.

17. Micromixer according to claim 15 or 16, characterized in that the length of the microchannels (30) decreases from stage i to stage i + 1.

18. Micromixer according to one of claims 15 to 17, characterized in that the bifurcation cascade is self-similar.

19. Micromixer according to one of claims 15 to 18, characterized in that at least one flat plate (2) on at least one of its two sides (26, 27) has microchannels (30) forming grooves (24).

20. Micro mixer according to claim 19, characterized in that the flat plate on both sides (26, 27) each has at least one bifurcation cascade, the micro-channels (30) opening into the opening (7) of the plate on one and the other side ( 26, 27) are arranged offset to one another.

21. Micro mixer according to claim 19 or 20, characterized in that the grooves (24) of each feed element (2) have a partial cross section of the microchannels (30) and the grooves (24) located in the superimposed surfaces (26, 27) are in the full cross section supplement the microchannels (30).

22. Micromixer according to one of claims 15 to 21, characterized in that the bifurcation cascades are each connected to a feed channel (4a, b) which are arranged in the feed elements (2).